Megger CM500 User manual

User Guide
M
CM500
Multi-Function Installation Tester

Safety Warnings 3
Initial Setup 4
General Description 6
Features, Controls and Connections 8
Operation 10
Backlight 10
Auto shut-off 10
Switched probe SP2 10
Checking Earth Potential 10
Voltage and Frequency Measurement 10
Polarity Indication 11
Determining Phase Sequence 12
Continuity Testing and Low Resistance measurement 12
Test Lead Resistance Nulling 12
Low Resistance Continuity measurement 13
Continuity Bleeper 13
Low input resistance voltmeter 13
5ΩThreshold 13
Insulation Testing and High Resistance measurement 14
Loop Impedance Measurement 15
Bonded Metalwork Testing 16
Prospective Short Circuit Current (PSCC) 17
PFC measurement accuracy 17
Earth Loop Resistance measurement at 15 mA 17
RCD Testing 18
No Trip Tests 20
Trip Tests 20
Auto Sequence RCD Test 22
Earth Resistance Measurement 24
Earth Electrode Resistance Measurement 24
Condition and Warning Indication 26
Test Results, Storage, Deletion and Retrieval 27
Serial Cable Connections 30
Specification 31
Accessories 35
Publications 36
Basic and Service Error calculation 37
Repair and Warranty 39
Symbols used on the instrument
Caution: Refer to accompanying notes
Equipment protected throughout by
Double or reinforced Insulation (Class II)
Equipment complies with current EU
Directives
Complies with IEC / EN 61557
2
Contents

3
SAFETY WARNINGS
QSafety Warnings and Precautions must be read and understood before the instrument is used. They must be observed
during use.
QThe circuit under test must be switched off, de-energised and isolated before test connections are made when carrying
out insulation and continuity tests.
QContinuity of protective conductors and earthed equipotential bonding of new or modified installations must be verified
before carrying out an earth fault loop impedance test, or RCD test.
QCircuit connections and exposed metalwork of an installation or equipment under test must not be touched.
QDo not move the rotary selector switch position while a test is in progress.
QThe LCD ‘neon’ voltage indicators cannot reveal a Neutral - Earth reversal.
QAfter insulation tests, capacitive circuits must be allowed to discharge before disconnecting test leads.
QThe instrument should not be used if any part of it is damaged.
QTest leads, probes and crocodile clips must be in good order, clean and with no broken or cracked insulation.
QU.K. Safety Authorities recommend the use of fused test leads when measuring voltage on high energy systems.
QReplacement fuses must be of the correct type and rating.
NOTE
THE INSTRUMENT MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS

Read this page before using the CM500.
Your CM500 has been set up as shown on the label on the
front of this User Guide:-
The first line gives the setting, which modifies the way the
instrument behaves.
The second line gives the printer report language. This may be
Language 1, which is English, or Language 2 which is the
language noted on the third line of the label.
Instrument Setup
The instrument setup mode allows you to change the setting, the
printer speed and the printer report language.
To display the current setup modes:-
1. Press and hold the backlight key,then turn the rotary
selector switch from the from ‘OFF’position to the ‘RCL’
position. The code (printer speed) is displayed.
2. Release the backlight key.
3. Toggle the Ikey to scroll through and display the current
setup modes. as follows:-
To change the Printer speed
1. Toggle the Ikey to scroll through and display the
code.
2. Press the SAVE key. The current speed setting is
displayed.
3. Toggle the RCL keys until the required speed setting is
displayed.
4. To save the new setting, press the SAVE key. The bleeper
sounds and is displayed. To abort the new setting, press
the EXIT key. is displayed.
To select the Printer language
1. Toggle the Ikey to scroll through and display the
code.
Initial Setup
4

2. Press the SAVE key. The current printer report language is
displayed as 1(English) or 2(as given on the type label on
the previous page).
Note:- Language 2can be changed using the CM500 Setup
Disk supplied.
3. Toggle the Ikey until the required language setting is
displayed.
4. To save the new setting, press the SAVE key. The bleeper
sounds and is displayed. To abort the new setting,
press the EXIT key.is displayed.
To select the Setting
1. Toggle the Ikey to scroll through and display the
code.
2. Press the SAVE key. The current setting is displayed as A
(Continental Europe) or b(U.K.).
3. Toggle the Ikey until the required setting is displayed.
4. To save the new setting, press the SAVE key. The bleeper
sounds and is displayed. To abort the new setting,
press the EXIT key.is displayed.
CM500 Setup Disk
The program on the disk enables the second printer language to
be changed into any of the separate languages. The program
may be run directly from disk. Connect the PC to the instrument
via a serial lead.
for DOS type: a:\cm500set and press: Return.
for Windows™ 3.1 or 3.11:
1. From the Program Manager options, select: File
2. From the options given, select: Run.
3. Type: a:\cm500set and press: Return.
For Windows™ 95:
1. Select the Start menu.
2. Select the Run option.
3. Type: a:\cm500set and press: Return.
Follow the instructions given by the program.
5

The MEGGER CM500 Multi-function Installation Tester is a
compact instrument designed to perform all of the functions
required by the electrical contractor to fully test domestic,
commercial and industrial wiring. Specially designed to comply
with U.K., European and other International wiring regulations
and standards, the CM500 may be used on all single and three
phase systems with rated voltages up to 300 Volts a.c. rms to
earth/ground.
Measured values are indicated on a large backlit analogue/digital
LCD and may also be stored in internal memory for later recall to
the display, direct printing via a standard serial printer, or
downloaded to a PC for storage, analysis and report generation.
The CM500 is supplied as standard in a protective test and carry
case, and with the necessary mains plug lead and 2-wire lead set
required to commence testing. Optional accessories include the
SP2,a2-wire lead set with test switch built into one of the probes
providing remote operation, and a 5 metre 2-wire lead set for
increased accessibility.
Key Features
•No Trip loop Impedance test
•Storage of test results in memory
•Direct serial printer driver output
•RS-232 Output for PC storage
•Recall stored results to the display
•RCD Ramp test function
•Analogue arc and digital display.
•Selectable backlight
•Optional switchable probe (SP2)
Test Capability
• Insulation
Test voltages of 250V, 500V and 1000V.
• Continuity testing
Fast bleeper
Test lead resistance nulling
Automatic polarity reversal (Setting A)
• Loop Testing
Operates regardless of mains polarity (Setting A)
Two wires only needed for testing
Automatic test start on voltage detection
Direct indication of short circuit current.
Phase - phase, phase - neutral & phase - earth tests
Simple earth electrode test
•RCD Tests
Tests selective (delayed) general and d.c. sensitive RCDs.
Two wires only needed for testing
Contact voltage and loop resistance displayed.
Selectable test current for programmable devices
• Supply voltage and frequency measurement
• Phase sequence indication
• Mains outlet polarity indication
Application
The CM500 may be be connected live to earth or between live
conductors of systems that have a rated voltage of 300V a.c. rms
to earth and an installation (overvoltage) Category III or lower.
This means that the CM500 may be connected to any fixed
wiring of a building installation, but not to primary supply circuits
such as overhead cables. To maintain user safety and ensure
accurate measurements, only use the test leads supplied or
General Description
6

recommended for use with this instrument.
The CM500 is fuse protected to 440V 10kA. The maximum
current which could flow through this fuse in the case of a fault is
limited to 10 kA by the impedance of the test leads. There is a
fuse accessible in the battery compartment which protects the
Insulation and Continuity range. If warning of a ruptured fuse is
given during a test, and if the warning symbol is present when
attempting to carry out an insulation test with the test leads
shorted together, this fuse must be replaced by another fuse of
the same type and rating i.e. 500 mA (F) 500 V H.B.C. 10 kA.
Fuse Replacement
To replace the fuse, disconnect the test leads,switch the
instrument Off and with a screwdriver, loosen the captive screw
holding the battery compartment cover in place. Remove the
cover. Depress the fuseholder slightly, and turn a quarter turn
anti-clockwise to release. Remove the holder and replace the
fuse with one of the correct size and rating. Relocate the fuse
holder,depress and turn a quarter turn clockwise. Replace and
re-secure the cover.
Battery Replacement
When the low battery symbol appears, the cells are nearly
exhausted and should be replaced as soon as possible. When
the battery is exhausted, the instrument will not perform tests
and the cells must be replaced. Use Alkaline cells IEC LR6 (AA)
or 1,5 V nickel cadmium cells only.
To install or replace the cells, disconnect the test leads,switch
the instrument Offand loosen the captive screw holding the
battery compartment cover in place. Remove the cover,lift out
and disconnect the battery holder to access the cells. Ensure
that the replacement cells are fitted with the correct polarity,in
accordance with the symbols on the battery holder moulding.
Carefully re-connect the battery holder to the plug, replace the
battery holder in the compartment, and re-secure the cover.
Remove the cells if the instrument is not going to be used for any
extended period of time. Stored results are retained when the
battery is disconnected.
Test Leads
All test leads form part of the measuring circuit of the instrument
and must not be modified or changed in any way,or be used with
any other electrical instrument or appliance. The power cord
supplied with the CM500 is a test lead that forms part of the
measuring circuit of the instrument. The overall length of this lead
must not be altered. If the power cord plug is not suitable for your
type of socket outlets, do not use an adaptor. You may change
the plug once only by cutting the cord as close to the plug as
possible and fitting a suitable plug.
The colour code of the cord is:
Earth (Ground) Yellow/Green
Neutral Blue
Phase (Line) Brown
Note: A plug severed from the power cord must be destroyed, as
aplug with bare conductors is hazardous in a live socket outlet.
7
Incorrect battery cell polarity
can cause electrolyte leakage,
resulting in damage to the
instrument.

8
Features, Controls and Connections
Press Iand TYPE key to:
• Select test parameters
• Enter test result identification
Auto Shut-off
Operates after 5 minutes of
inactivity by the instrument
(30 seconds in Bleeper mode)
Turn Rotary Selector Switch to:
• Select test position
• Select Download (RCL)
• Select ‘OFF’
Press TYPE key to:
• Select test voltage (MΩ)
• Select type of RCD
• Delete data (in combination
with Ikey)
Insulation test positions
Continuity test position
VAR test selection
Push TEST button to:
• Initiate the selected test
• Repeat selected test
Touch finger to Earth Test Pad to:
•Check potential between the Earth
connection and your finger
Press key to:
• Display other test results
Press and hold key to:
• Save test results
RCD test selection
Backlight key
Continuity Bleeper position
Lead resistance null
position
Recall / Download position
‘OFF’ position
150mA 40ms test selection
Loop test selection

9
Fuse
Ruptured
Low Battery
voltage indication
3Phase
sequence
RCD Test
Selection
RCD Type
Selection
Lead resistance
null ‘On’
Over / Under
Range
Excessive
Noise
Single Phase
Polarity indication
Plug polarity
Thermal
Trip operated
Touch button -
Earth >100 V.
CM500 Display
CM500 Connections

Backlight
The display backlight gives a clear display of measurements in
poor lighting conditions. The backlight will briefly operate when
the CM500 is switched on. To switch the backlight on, press the
key. Press the key again to switch the backlight off.
To conserve battery power, the backlight will automatically switch
off after a period of 15 seconds (if the battery voltage is low, this
period is automatically reduced).
Auto Shut - Off
To extend battery life and reduce unnecessary drainage, the
CM500 uses advanced battery management techniques,
switching functions off when they are not required. For example,
if an external voltage of 25 V or less is applied, no value is
displayed unless the backlight is switched on. After a period of
inactivity by the instrument, the CM500 will switch itself off,
preceded by a series of bleeps. Toswitch the instrument back
on, press any key.
Switched Probe SP2
This is an accessory which can be used anywhere that the 2-wire
lead set is specified in this User Guide. The press button probe
duplicates the function of the TEST key on the instrument,
allowing quick and easy testing.
Checking Earth Potential
To quickly distinguish live and earth, this feature provides display
indication if a voltage greater than 100 V exists between the
earth connection and your finger.
1. In any switch position except OFF,RCL and (Ω),
connect the earth connection (black for the 2-wire lead
set, green for the 3-wire lead set) to earth.
2. Touch a finger to the metal pad on the front panel. This
is safe and will not endanger you.
3. If a voltage greater than 100 V exists between the finger
(normally at earth potential) and the earth wire, the
warning symbol is displayed.
Voltage and Frequency Measurement
The CM500 will display the supply voltage and frequency in all
switch positions except (Ω),RCL and OFF.The DISPLAY
key will alternate between voltage and frequency.
Power plug connection
1. Insert the power cord plug into an installation socket.
2. Supply voltage and polarity are displayed.
3. Press DISPLAY to alternate between supply voltage and
frequency.
2-wire lead set connection
If an installation socket is not available, use the 2-wire lead set.
1. Connect the red and black leads to the two conductors to
be tested.
2. Voltage between the leads and polarity are displayed.
Note:- Though displayed, when using the 2-wire test set, ‘neon’
Operation
10
The SP2 probe test key circuit is hazardous live
during a test. It is safe in normal use.
Continuity of the SP2 probe non replaceable fuse must be
confirmed (by testing in the Bleeper range) before making any
measurement.